Hybrid vehicle thermal management using a bypass path in a catalytic converter unit

ABSTRACT

A hybrid vehicle includes an exhaust gas treatment system having a bypass valve for directing a flow of air or exhaust gas through a bypass path or through a primary catalyst. The hybrid vehicle includes an internal combustion engine and an electric motor, each selectively engageable with a transmission to provide a drive torque. The electric motor spins the internal combustion engine when engaged to provide the drive torque, thereby creating a flow of unheated air from the internal combustion engine that flows through the exhaust gas treatment system. The bypass valve directs the flow of air through the bypass path when the engine is spinning and not fueled to prevent cooling of the primary catalyst. The bypass valve directs the flow of exhaust gas through the primary catalyst when the internal combustion engine is spinning and is being fueled, i.e., running, to treat the flow of exhaust gas.

TECHNICAL FIELD

The invention generally relates to a hybrid vehicle and a method of operating the hybrid vehicle to maintain thermal efficiency of a catalyst of an exhaust gas treatment system for an internal combustion engine when the internal combustion engine is spinning, but is not being fueled.

BACKGROUND

Hybrid vehicles with an Internal Combustion Engine (ICE) include an exhaust gas treatment system for reducing the toxicity of the exhaust gas from the engine. The treatment system typically includes a catalytic converter unit, which includes a catalyst that reduces nitrogen oxides in the exhaust gas to nitrogen and carbon dioxide or water, as well as oxidizes carbon monoxide (CO) and unburnt hydrocarbons (HCs) to carbon dioxide and water. The catalyst may include, but is not limited to, Platinum Group Metals (PGM). The catalyst must be heated to a light-off temperature of the catalyst before the catalyst becomes operational. Accordingly, the exhaust gas must heat the catalyst to the light-off temperature before the reaction between the catalyst and the exhaust gas begins.

The hybrid vehicle may further include an electric motor. The internal combustion engine and the electric motor may each be selectively engaged to power the vehicle, i.e., the internal combustion engine and the electric motor may each be selectively engaged to generate a drive torque for a transmission. When the electric motor is being engaged to provide the drive torque to the transmission, the internal combustion engine is typically not being fueled and is not running However, because both the electric motor and the internal combustion engine are coupled to the transmission to provide the drive torque to the transmission, the electric motor may cause the internal combustion engine to spin when the electric motor is engaged to provide the drive torque. When the internal combustion engine is being spun while the electric motor is providing the drive torque, the internal combustion engine produces a flow of air which is directed through the exhaust gas treatment system. This flow of air is not heated, and cools the components of the exhaust gas treatment system, including the catalyst. If the catalyst is cooled to a temperature below the light-off temperature, then the exhaust gas from the internal combustion engine, once fueled and running, may not be properly treated.

SUMMARY

A method of operating a hybrid vehicle is provided. The method includes determining if an internal combustion engine is spinning or is not spinning, determining if the internal combustion engine is being fueled to generate a drive torque when the internal combustion engine is spinning, or is not being fueled when the internal combustion engine is spinning, and directing a flow of air created by the internal combustion engine through a bypass path that bypasses a primary catalyst to prevent the flow of air from cooling the primary catalyst when the internal combustion engine is spinning and is not being fueled.

A method of operating a hybrid vehicle is also provided. The method includes determining if an internal combustion engine is spinning or is not spinning, determining if the internal combustion engine is being fueled to generate a drive torque when the internal combustion engine is spinning, or is not being fueled when the internal combustion engine is spinning When the internal combustion engine is spinning and is not being fueled a bypass valve of an exhaust gas treatment system is opened to direct a flow of air created by the internal combustion engine through a bypass path that bypasses a primary catalyst to prevent the flow of air from cooling the primary catalyst. When the internal combustion engine is spinning and is being fueled, the bypass valve is closed to direct a flow of exhaust gas created by the internal combustion engine through the primary catalyst to treat the flow of exhaust gas. The method further includes sensing a temperature of the primary catalyst when the engine is spinning and is being fueled, determining if the sensed temperature of the primary catalyst is greater than a pre-defined temperature, and at least partially opening the bypass valve when the temperature of the primary catalyst is greater than a pre-defined limit to divert at least a portion of the flow of exhaust gas created by the internal combustion engine through the bypass path to prevent the primary catalyst from overheating when the engine is spinning and is being fueled. The method further includes treating the flow of exhaust gas diverted through the bypass path when the temperature of the primary catalyst is greater than the pre-defined limit with a second downstream catalyst.

A vehicle is also provided. The vehicle includes a transmission configured for receiving a drive torque and transmitting the drive torque to a drive wheel. An internal combustion engine is coupled to the transmission, and is configured for selectively supplying the drive torque to the transmission. An exhaust gas treatment system is coupled to the internal combustion engine, and is configured for treating a flow of exhaust gas created by the internal combustion engine when the internal combustion engine is being fueled. An electric motor is coupled to the transmission and configured for selectively supplying the drive torque to the transmission. When the electric motor is supplying the drive torque to the transmission, the electric motor spins the internal combustion engine in an un-fueled state, thereby creating a flow of unheated air through the exhaust gas treatment system. The exhaust gas treatment system includes a primary catalyst, a bypass path defining a fluid flow path that bypasses the primary catalyst, and a bypass valve configured for controlling fluid flow between the primary catalyst and the bypass path. The bypass valve is disposed in an open position to direct air flow through the bypass path when the electric motor is supplying the drive torque to the transmission and spinning the internal combustion engine. The bypass valve is disposed in a closed position to direct the flow of exhaust gas from the internal combustion engine through the primary catalyst when the internal combustion engine is fueled and supplying the drive torque to the transmission.

Accordingly, when the electric motor is providing the drive torque for the transmission and thereby spinning the internal combustion engine, the flow of unheated air created by the internal combustion engine is directed through the bypass path, thereby bypassing the primary catalyst. Because the flow of unheated air is directed through the bypass path and not across or through the primary catalyst, the unheated air from the spinning internal combustion engine does not cool the primary catalyst, thereby preventing cooling of the primary catalyst to a temperature below a light-off temperature of the primary catalyst, and maintaining the thermal efficacy of the primary catalyst. The primary catalyst may therefore be ready to treat the exhaust gas from the internal combustion engine once the internal combustion engine is fueled and running

The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of an exhaust gas treatment system for an internal combustion engine of a hybrid vehicle.

FIG. 2 is a schematic cross sectional view of a catalytic converter unit of the exhaust gas treatment system.

FIG. 3 is a flow chart showing a method of operating the hybrid vehicle to maintain the thermal efficacy of a primary catalyst of an exhaust gas treatment system.

DETAILED DESCRIPTION

Referring to the Figures, wherein like numerals indicate like parts throughout the several views, a hybrid vehicle is shown generally at 20 in FIG. 1. Referring to FIG. 1, the hybrid vehicle 20 includes a transmission 22. The transmission 22 is configured for receiving a drive torque and transmitting the drive torque to a drive wheel (not shown). The transmission 22 may include but is not limited to an automatic transmission 22. The transmission 22 receives the drive torque from an internal combustion engine 24 and/or an electric motor 26. Both the internal combustion engine 24 and the electric motor 26 are coupled to the transmission 22 and configured for selectively supplying the drive torque to the transmission 22. The internal combustion engine 24 may include but is not limited to a gasoline engine or a diesel engine, and may include any suitable size and/or configuration suitable to satisfy output and performance requirements of the hybrid vehicle 20. The electric motor 26 may include any suitable size, style and/or configuration of electric motor 26 suitable to satisfy the output and performance requirements of the hybrid vehicle 20.

The hybrid vehicle 20 may engage either the internal combustion engine 24 or the electric motor 26 to generate the drive torque. The electric motor 26 supplies all of the drive torque when engaged. As such, when the electric motor 26 is engaged to exclusively supply the drive torque to the transmission 22, the electric motor 26 also spins the internal combustion engine 24. However, because the internal combustion engine 24 is not being engaged to supply the drive torque, the internal combustion engine 24 is not fueled. Accordingly, when the electric motor 26 is engaged to supply the drive torque, the electric motor 26 spins the internal combustion engine 24 in an un-fueled state. When the internal combustion engine 24 spins in the un-fueled state, the internal combustion engine 24 creates a flow of unheated air, which flows through an exhaust gas treatment system 28.

The exhaust gas treatment system 28 is coupled to the internal combustion engine 24. The treatment system 28 treats a flow of exhaust gas, indicated by arrow 30, from the internal combustion engine 24 when the internal combustion engine 24 is being fueled, i.e., when the internal combustion engine 24 is running The exhaust gas treatment system 28 treats the flow of exhaust gas from the internal combustion engine 24 to reduce the toxicity of the exhaust gas, i.e., to reduce toxic emissions of the exhaust gas, including but not limited to, nitrogen oxides (NO), carbon monoxide (CO) and/or hydrocarbons (HC).

The exhaust gas treatment system 28 includes a catalytic converter unit 32. The catalytic converter unit 32 is disposed downstream of the internal combustion engine 24. The catalytic converter unit 32 includes a primary catalyst 34. The primary catalyst 34 may include, but is not limited to, a three way catalyst. The primary catalyst 34 may include Platinum Group Metals (PGM), and convert a percentage of the nitrogen oxides in the exhaust gas into nitrogen and carbon dioxide or water, as well as oxidizes a percentage of the carbon monoxide to carbon dioxide and oxidizes a percentage of the unburnt hydrocarbons to carbon dioxide and water. The catalytic converter unit 32 also defines a bypass path 36. The bypass path 36 defines a fluid flow path that bypasses the primary catalyst 34. Referring also to FIG. 2, the primary catalyst 34 includes a tubular shape. The tubular shape is disposed annularly about and defines the bypass path 36, with the bypass path 36 extending along a central opening of the tubular shaped primary catalyst 34.

A bypass valve 38 is also disposed within the catalytic converter unit 32. The bypass valve 38 is configured for controlling fluid flow between the primary catalyst 34 and the bypass path 36. The bypass valve 38 is disposed upstream of the primary catalyst 34, and is configured for opening and closing fluid flow through the central region of the tubular shaped primary catalyst 34 defining the bypass path 36. The bypass valve 38 is moveable between an open position and a closed position. When the bypass valve 38 is disposed in the open position, the bypass valve 38 directs fluid flow, e.g., air and/or exhaust flow, through the bypass path 36. As such, when the electric motor 26 is exclusively supplying all of the drive torque to the transmission 22 and thereby spinning the internal combustion engine 24, the bypass valve 38 may be disposed in the open position to direct the flow of air through the bypass path 36, around and thereby bypassing the primary catalyst 34. When the bypass valve 38 is disposed in the closed position, the bypass valve 38 directs fluid flow, e.g., air and/or exhaust flow, through the primary catalyst 34. As such, when the internal combustion engine 24 is fueled to supply the drive torque, the bypass valve 38 may be disposed in the closed position to direct the flow of exhaust gas from the internal combustion engine 24 through the primary catalyst 34.

As shown, the catalytic converter unit 32 may further include a secondary catalyst 40. The secondary catalyst 40 is disposed downstream of the primary catalyst 34. The secondary catalyst 40 is configured to treat the flow of exhaust gas that flows through either the primary catalyst 34 or through the bypass path 36. Accordingly, if any exhaust gas from the internal combustion engine 24 is directed through the bypass path 36, then the secondary catalyst 40 treats the exhaust gas. The secondary catalyst 40 may include, but is not limited to, a three way catalyst. The secondary catalyst 40 may include Platinum Group Metals (PGM), and convert a percentage of the nitrogen oxides in the exhaust gas into nitrogen and carbon dioxide or water, as well as oxidizes a percentage of the carbon monoxide to carbon dioxide and oxidizes a percentage of the unburnt hydrocarbons to carbon dioxide and water.

Referring to FIG. 3, a method of operating the hybrid vehicle 20 described above is provided. The method is shown generally at 50 in FIG. 3. The method 50 includes determining if an internal combustion engine 24 is spinning or is not spinning, generally indicated by block 52. If the internal combustion engine 24 is determined to not be spinning, indicated at 54, and is not being fueled, the method 50 may include closing the bypass valve 38, generally indicated by block 56. If the internal combustion engine 24 is determined to be spinning, indicated at 58.

The method 50 may further include engaging the electric motor 26 to selectively generate the drive torque with the electric motor 26, generally indicated by block 60. As noted above, operation of the electric motor 26 also spins the internal combustion engine 24, thereby creating the flow of air from the internal combustion engine 24 that flows through the exhaust gas treatment system 28. Alternatively, the method 50 may further include fueling the internal combustion engine 24 to generate the drive torque, generally indicated by block 62. As noted above, fueling of the internal combustion engine 24, i.e., running the internal combustion engine 24, generates a flow of heated exhaust gas that must be treated.

The method further includes determining if the internal combustion engine 24 is being fueled or is not being fueled, generally indicated by block 64. When the internal combustion engine 24 is spinning, indicated at 58, the internal combustion engine 24 may also be fueled to generate the drive torque, indicated at 66. Alternatively, as described above, the internal combustion engine 24 may be spinning as a result of the electric motor 26 being engaged to generate the drive torque, and as such is not being fueled, indicated at 68.

When it is determined that the internal combustion engine 24 is spinning, indicated at 58, and is not being fueled, indicated at 68, then the method 50 may further include directing the flow of air created by the internal combustion engine 24 through the bypass path 36, generally indicated by block 70, to bypass the primary catalyst 34. Directing the flow of unheated air around the primary catalyst 34, thereby bypassing the primary catalyst 34, prevents the flow of air from cooling the primary catalyst 34. Accordingly, the primary catalyst 34 may remain at a pre-heated temperature, ready to react with exhaust gas from the internal combustion engine 24 when the internal combustion engine 24 is fueled. Directing the flow of air created by the internal combustion engine 24 through the bypass path 36 may further be defined as opening the bypass valve 38 to direct the flow of air created by the internal combustion engine 24 through the bypass path 36. However, it should be appreciated that the flow of air from the internal combustion engine 24 may be directed through the bypass path 36 in some other manner not shown or described herein.

When it is determined that the internal combustion engine 24 is spinning, indicated at 58, and is being fueled, indicated at 66, then the method 50 may further include directing the flow of exhaust gas created by the internal combustion engine 24 through the primary catalyst 34, generally indicated by block 72, to treat the flow of exhaust gas. Directing the flow of exhaust gas created by the internal combustion engine 24 through the primary catalyst 34 may further be defined as closing the bypass valve 38 to direct the flow of exhaust gas created by the internal combustion engine 24 through the primary catalyst 34. However, it should be appreciated that the flow of exhaust gas from the internal combustion engine 24 may be directed through the primary catalyst 34 in some other manner not shown or described herein.

The method 50 may further include sensing a temperature of the primary catalyst 34, generally indicated by block 74. The temperature of the primary catalyst 34 may be sensed in any appropriate manner, including but not limited to sensing the temperature of the primary catalyst 34 with a temperature sensor disposed in the catalytic converter unit 32. The temperature of the primary catalyst 34 may be sensed at any time, but it is particularly important to sense the temperature of the primary catalyst 34 when the engine is spinning and is being fueled. The useful life expectancy of the primary catalyst 34 may be reduced if the temperature of the primary catalyst 34 is overheated. Accordingly, the method 50 includes determining if the sensed temperature of the primary catalyst 34 is greater than a pre-defined temperature, generally indicated by block 76. The pre-defined temperature is an upper operational temperature of the primary catalyst 34. The pre-defined temperature is a temperature that is set to a level that ensures the primary catalyst 34 does not overheat. Accordingly, so long as the primary catalyst 34 is at or below the pre-defined temperature, the primary catalyst 34 should not overheat.

In order to ensure that the primary catalyst 34 does not overheat when the temperature of the primary catalyst 34 is greater than the pre-defined limit, indicated at 78, the method 50 may further include at least partially opening the bypass valve 38, generally indicated by block 80. Opening the bypass valve 38 diverts at least a portion of the flow of exhaust gas created by the internal combustion engine 24 through the bypass path 36, which prevents the primary catalyst 34 from overheating. The flow of exhaust gas diverted through the bypass path 36 is then treated with the secondary catalyst 40. When the temperature of the primary catalyst 34 is less than the pre-defined limit, indicated at 82, the method 50 may further include maintaining the bypass valve 38 in the closed position, generally indicated by block 84.

While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims. 

1. A method of operating a hybrid vehicle, the method comprising: determining if an internal combustion engine is spinning or is not spinning; determining if the internal combustion engine is being fueled to generate a drive torque when the internal combustion engine is spinning, or is not being fueled when the internal combustion engine is spinning; and directing a flow of air created by the internal combustion engine through a bypass path that bypasses a primary catalyst to prevent the flow of air from cooling the primary catalyst when the internal combustion engine is spinning and is not being fueled.
 2. A method as set forth in claim 1 further comprising directing a flow of exhaust gas created by the internal combustion engine through the primary catalyst to treat the flow of exhaust gas when the internal combustion engine is spinning and is being fueled.
 3. A method as set forth in claim 2 wherein directing the flow of air created by the internal combustion engine through the bypass path is further defined as opening a bypass valve to direct the flow of air created by the internal combustion engine through the bypass path.
 4. A method as set forth in claim 3 wherein directing the flow of exhaust gas created by the internal combustion engine through the primary catalyst is further defined as closing the bypass valve to direct the flow of exhaust gas created by the internal combustion engine through the primary catalyst.
 5. A method as set forth in claim 1 further comprising sensing a temperature of the primary catalyst.
 6. A method as set forth in claim 5 wherein sensing the temperature of the primary catalyst is further defined as sensing the temperature of the primary catalyst when the engine is spinning and is being fueled.
 7. A method as set forth in claim 6 further comprising determining if the sensed temperature of the primary catalyst is greater than a pre-defined temperature.
 8. A method as set forth in claim 7 further comprising at least partially opening the bypass valve when the temperature of the primary catalyst is greater than a pre-defined limit to divert at least a portion of the flow of exhaust gas created by the internal combustion engine through the bypass path to prevent the primary catalyst from overheating.
 9. A method as set forth in claim 8 further comprising treating the flow of exhaust gas diverted through the bypass path when the temperature of the primary catalyst is greater than the pre-defined limit with a second downstream catalyst.
 10. A method as set forth in claim 1 further comprising closing the bypass valve when the internal combustion engine is not spinning and is not being fueled.
 11. A method as set forth in claim 1 further comprising selectively generating a drive torque with an electric motor, whereby the electric motor spins the internal combustion engine thereby creating a flow of air from the internal combustion engine that flows through the exhaust gas treatment system.
 12. A method as set forth in claim 1 further comprising fueling the internal combustion engine to generate a drive torque.
 13. A method of operating a hybrid vehicle, the method comprising: determining if an internal combustion engine is spinning or is not spinning; determining if the internal combustion engine is being fueled to generate a drive torque when the internal combustion engine is spinning, or is not being fueled when the internal combustion engine is spinning; opening a bypass valve of an exhaust gas treatment system to direct a flow of air created by the internal combustion engine through a bypass path that bypasses a primary catalyst to prevent the flow of air from cooling the primary catalyst when the internal combustion engine is spinning and is not being fueled; closing the bypass valve to direct a flow of exhaust gas created by the internal combustion engine through the primary catalyst to treat the flow of exhaust gas when the internal combustion engine is spinning and is being fueled; sensing a temperature of the primary catalyst when the engine is spinning and is being fueled; determining if the sensed temperature of the primary catalyst is greater than a pre-defined temperature; at least partially opening the bypass valve when the temperature of the primary catalyst is greater than a pre-defined limit to divert at least a portion of the flow of exhaust gas created by the internal combustion engine through the bypass path to prevent the primary catalyst from overheating when the engine is spinning and is being fueled; and treating the flow of exhaust gas diverted through the bypass path when the temperature of the primary catalyst is greater than the pre-defined limit with a second downstream catalyst.
 14. A method as set forth in claim 13 further comprising selectively generating a drive torque with an electric motor, whereby the electric motor spins the internal combustion engine thereby creating a flow of air from the internal combustion engine that flows through the exhaust gas treatment system.
 15. A vehicle comprising: a transmission configured for receiving a drive torque and transmitting the drive torque to a drive wheel; an internal combustion engine coupled to the transmission and configured for selectively supplying the drive torque to the transmission; an exhaust gas treatment system coupled to the internal combustion engine and configured for treating a flow of exhaust gas created by the internal combustion engine when the internal combustion engine is being fueled; an electric motor coupled to the transmission and configured for selectively supplying the drive torque to the transmission; wherein the electric motor spins the internal combustion engine in an un-fueled state thereby creating a flow of unheated air through the exhaust gas treatment system when the electric motor is supplying the drive torque to the transmission; the exhaust gas treatment system including: a primary catalyst; a bypass path defining a fluid flow path that bypasses the primary catalyst; and a bypass valve configured for controlling fluid flow between the primary catalyst and the bypass path; wherein the bypass valve is disposed in an open position to direct air flow through the bypass path when the electric motor is supplying the drive torque to the transmission and spinning the internal combustion engine, and wherein the bypass valve is disposed in a closed position to direct the flow of exhaust gas from the internal combustion engine through the primary catalyst when the internal combustion engine is fueled and supplying the drive torque to the transmission.
 16. A vehicle as set forth in claim 15 wherein the primary catalyst, the bypass path and the bypass valve are all disposed within a catalytic converter unit.
 17. A vehicle as set forth in claim 16 wherein the catalytic converter unit includes a second downstream catalyst disposed downstream of the primary catalyst.
 18. A vehicle as set forth in claim 17 wherein the primary catalyst includes a tubular shape disposed annularly about and defining the bypass path, with the bypass path extending along a central opening of the tubular shaped primary catalyst.
 19. A vehicle as set forth in claim 18 wherein the bypass valve is disposed upstream of the primary catalyst and is configured for opening and closing fluid flow through the central region of the tubular shaped primary catalyst defining the bypass path. 